Handbook b5 transport in plants

Agastya International Foundation

Transport in Plants Handbook B5

“It is not enough to discover and prove a useful truth previously unknown, but that it is necessary also to be able to propagate and get it recognized.�

-Jean Baptiste Lamarck (1744-1829)

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Handbook – B5 Transportation in Plants OVERVIEW OF HANDBOOK ABL

CONCEPT

ABL1

Processes involved in transportation in plants

ABL2

Transport of food and water in plants

NO. OF ACTIVITIES 8

TIME (min)

6

ABLs WITH REFERENCE TO STANDARD SERIAL NUMBER 1 2

STANDARD 9, 10 9, 10

RELEVANT ABL ABL1 ABL2

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PAGE NO. 3

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LIST OF FIGURES, CHARTS AND WORKSHEETS

S. No Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 Figure 12 Figure 13 Figure 14 Figure 15 Figure 16 Figure 17 Chart 1 Chart 2 Chart 3 Chart 4 Chart 5 Chart 6 Worksheet 1

Name Roots absorb water Diffusion of solids in liquids Diffusion of liquids in liquids Diffusion of liquids in air Diffusion of gasses Potato Osmometer Direction of flow in Xylem and phloem Glass slide exp. A Glass slide exp. B Capillary exp.

Thermocol ball exp.

Capillary action Adhesion and cohesion Adhesion and cohesion - leaf Capillary transfer exp.

Girdling of a plant Xylem and Phloem Bees in a box – Flip chart Concentration gradient chart Difference between diffusion, osmosis and active transport Xylem, Phloem and Root hair – flip chart - Microscopic images Root hair and cells Reading between the rings - flip chart Plant template worksheet

Page No 10 8 9 9 9 12 24 29 29 29 30 30 31 31 32 33 34 6 16 17 22 26 35 23

Note to Instructor: All the figures in this handbook are for the Instructor’s reference only. The Charts need to be printed and shown to the learners during the course of the activity. Worksheets need to be printed out in advance for the students. The number of worksheets required is mentioned in the Material List.

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ABL 1 - Processes involved in transportation Activity

Learning Objective

Key Messages 

1.1

What is Imbibition?

Imbibition is a surface phenomenon by which substances absorb water.

Imbibition aids in many life processes like germination of seeds.

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

1.2

What is diffusion?







1.3

What is osmosis?

 

  1.4

What is active transport?

 

Time (min) 5

Diffusion is the movement of molecules/particles of matter from the region of their higher concentration to the region of their lower concentration Diffusion occurs across different media - solid in liquid, solid in gas, liquid in liquid, liquid in gas and gas in gas.

Movement of molecules is essential for diffusion to occur

30

Osmosis is the diffusion of water molecules across a semi permeable membrane.

Osmosis is a key process involved in transportation in living things.

Osmosis also has many practical applications in our surroundings today.

15

Active transport is the passage of a substance (salt or ion) from its lower to higher concentration.

Direction of Active transport is opposite to diffusion.

This uses energy from ATP to transport ions and molecules across a living membrane.

Active Transport is essential to transport food and mineral ions in many living things.

15

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4

ABL 1.1

Time: 5 min

LEARNING OBJECTIVE - What is Imbibition?

ADVANCE PREPARATION: Material List S. No.

Material

Quantity

1

Beans (Rajma)

50 gms per class

2

Bowls

2 per class

3

Plastic bottle with lid

2 per class

Things to Do Half the beans must be soaked about 8 hours before the experiment. Keep the remaining beans in the second bowl without soaking.

Safety Precautions Not Applicable

SESSION: Link to known information/previous activity We know that plants need food and water. Let us see how the plant gets them from the surroundings and transports them.

Procedure Put the soaked beans without the water in one bottle with a lid and pass it around the class. Do the same with the un-soaked beans. Then, ask two volunteers to come forward and touch the soaked and un-soaked beans and describe their observations to the class.

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Leading Questions 1. Why do you think the beans looked different?

2. How do you think the water entered the beans?

3. Do you know the use of the processes of imbibition?

Discussion and Explanation 1. The beans looked different because some of them had taken in water.

2. The beans, through a surface phenomenon called imbibition, absorbed the water. This process occurs in living and non-living things.

3. Imbibition makes the seed swell up and helps in processes like breaking the seed coat to help in germination.

KEY MESSAGES:  

Imbibition is a surface phenomenon by which substances absorb water.

Imbibition aids in many life processes like germination of seeds.

LEARNING CHECK: Ask learners to list the key things they have learnt. Guide them to the key messages listed and then put up the key messages chart.

Time: 30 min

ABL 1.2 LEARNING OBJECTIVE -What is diffusion?

ADVANCE PREPARATION: Material List SL.NO. 1 2 3 4 5

Material Pictures of bees in a box (set of 3 pictures) – Flip chart 1 Potassium permanganate crystals Beakers (250 ml) Water Spray bottle

Quantity 1 per class 4-5 per class 4-5 per class 1000ml per class 1 per class

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6 7 8 9 10 11

Food colouring / dye Agarbatti / incense sticks Small herbaceous plant with roots (Coriander/Mint/ Palak) Test tube (Boiling) Any Vegetable Oil Marker Pen

Few drops per class 1 per class 2 per class 3 per class 10ml per class 1 per class

Things to Do Clean the roots of the plant and keep them moist.

Safety Precautions Not Applicable

SESSION

SESSION 1.2a Note to Instructor – Set up the experiment for session 1.2c before you start this activity.

Link to known information/previous activity While our experiment with the plants is going on, let us understand how molecules move.

Procedure Note to Instructor – This activity is to show students that molecules are in a constant state of motion.

This leads to them moving from a region of higher concentration to a region of lower concentration. This is the process of diffusion.

Put up Chart 1 and show learner’s pictures 1 and 2 and ask them to describe what they see in the picture, using the leading questions below.

[Chart 1 – Picture 1] One side of the box has bees and the other side does not.

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UNDERSTANDING THE ACTIVITY: Leading Questions 1.

2.

3.

4.

Why do you think all the bees are on one side of the box in picture 1?

What do you think will happen if the screen was removed?

If the box had no screen, how do you think the bees will be in the box?

The bees move through the air when the screen is removed. Imagine that each of these bees represents molecules of a substance and air in the box is the medium. So, now can you tell me what diffusion is?

Discussion and Explanation 1. The bees are all on one side only as the screen stops them from going to the other side. There is a higher concentration of bees on one side of the screen.

2. If the screen is removed, some of the bees will go to the other side where there is space and the bees will uniformly occupy the whole box Show picture 2 – bees filled in the box.

[Chart 1 – Picture 2] Bees fill up the box, as there is no screen.

3. If the box had no screen the bees would always spread out throughout the box.

4. If we compare the movement of bees with molecules, diffusion is the movement of molecules through a medium, by which they are uniformly distributed though the given space. Movement occurs from a region of higher concentration of molecules to lower concentration.

KEY MESSAGES:

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

Diffusion is the movement of molecules/particles of matter from the region of their higher concentration to the region of their lower concentration.

LEARNING CHECK: Show learners the below picture and ask them which direction the bees will move if the screen were to be removed now. Right to left or left to right?

[Chart 1 – Picture 3] (Answer for Instructor’s reference: The bees will move from left to right if you are facing the picture. They will move from the region of higher concentration to the region of lower concentration) SESSION: 1.2b Link to known information/previous activity In the previous activity, 1.2a we learnt the meaning of diffusion. Now we will look at the different mediums in which diffusion can take place.

Procedure Divide the learners into 5 to 6 groups. Each group will now do a set of four experiments with your help. Tell them to number the experiments. In each experiment, they should write down what molecule is diffusing, and in what medium.

In the ‘bees in the box’ example, the Bees were the “molecules” that were diffusing and the medium was air.

Ask each group to do the following experiments and note down their observations after each experiment: 1) Experiment 1: Give each group a beaker of water and one crystal of potassium permanganate.

Ask them to drop the crystal in the water.

2) Experiment 2: In the same beaker, ask them to take fresh water and add few drops of dye/food colour in each.

3) Experiment 3: Use the spray bottle to squirt out a jet of water.

4) Experiment 4: Light the agarbatti/incense stick.

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UNDERSTANDING THE ACTIVITY: Leading Questions 1. What is taking place in the each experiment? What is the state of matter of the diffusing molecules and the medium in each case?

2. What conclusion can we draw from all these experiments put together?

3. Can we have a solid medium for diffusion? Why? Discussion and Explanation 1. In the first case, solid molecules of potassium permanganate undergo diffusion in water which is a liquid.

Figure 2 – Diffusion of solids In the second case, liquid food colouring diffuses in liquid water

Figure 3 – Diffusion of liquid in liquid In the third case, liquid water diffuses through air which is in gaseous state.

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Figure 4 – Diffusion of liquid in air In the fourth case, gaseous incense particles diffuse through air which is also in gaseous state.

Figure 5 – Diffusion in gasses 2. From all these cases we can come to the conclusion that diffusion can occur across various mediums like solid in liquid, liquid in liquid, solid in gas, gas in gas and gas in liquid.

3. No, we cannot have diffusion in a solid medium as there is no space for free movement of particles, which is essential for diffusion to take place.

SESSION 1.2c Note to Instructor – Setup this experiment in front of the learners before you start 1.2a and then tell them you will come back to discuss it later in the correct order after finishing 1.2b.

Link to known information/previous activity Now that we know what diffusion means, let us see the most important application of diffusion.

Procedure

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Set up the demo experiment as follows.

Figure 1 - Roots absorb water

1) Fill three test tubes with equal levels of water.

2) Put the plant in two of the test tubes. Leave the third empty as a control.

3) Put a small layer of oil using a dropper on top of the water to prevent evaporation in all the test tubes. Do this very slowly along the sides of the test tube.

4) Mark the water level on the tubes.

5) Put one of the test tubes with the plant in it in the sun and leave the other two in the shade.

6) Leave this setup undisturbed for 20 minutes.

UNDERSTANDING THE ACTIVITY: Leading Questions 1.

2.

3.

4.

5.

What do you observe in the test tubes after 20 minutes?

Why do we put a layer of oil on top of the water in the experiment set up?

Why is there a drop in water level in only two test tubes?

Is the drop in water level same in both the test tubes that have plants?

Why is the drop in water level higher in the test tube that was kept in the sun?

Discussion and Explanation 1. The water level in the test tube with the plants has decreased.

2. Oil prevents water from evaporating into the air so that we can be sure that the drop in level is only because of absorption.

3. There is a drop in the water level because the roots have absorbed water. They do so using the fine root hairs on their surface.

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4. No. The drop in water level is higher in the test tube that was kept in the sun.

5. This is because the rate of transpiration from the plant is higher in direct sunlight. (This shows that the water absorbed by the root is lost from the leaves by way of a process called transpiration.)

Points to note:  Plants absorb water through the roots.  The roots have thousands of root hair that increase the surface area for absorption of water.

Note To Instructor -Since the discussion of this experiment will be after sessions, 1.2a and 1.2b you can add key message that diffusion is important for many processes like absorption of water by the root hair.

KEY MESSAGES:   

Diffusion is the movement of molecules/particles of matter from the region of their higher concentration to the region of their lower concentration Diffusion occurs across different media - solid in liquid, solid in gas, liquid in liquid, liquid in gas and gas in gas.

Movement of molecules is essential for diffusion to occur

LEARNING CHECK: Ask learners to list the key things they have learnt. Guide them to the key messages listed and then put up the key messages chart. Use the learning check given at the end of ABL 1.4 . This is to be done after completing ABL 1.4.

Time: 15 min

ABL 1.3 LEARNING OBJECTIVE –What is osmosis?

ADVANCE PREPARATION: Material List Sl. No. 1 2 3

Material Potato Knife Ball pins

Quantity 1 per class 1 per class 2 per class

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4 5 6 7 8

Sugar Water Shallow dish / beaker Marker Raisins

50g per class 500 ml per class 2 per class 1 per class 10 per class

Things to do 1. Prepare sugar solution by mixing the sugar in 200ml of water before the experiment.

2. Soak some raisins in water for about 30 minutes before the class 3. Just before the class, peel and cut the potato in half as shown in Figure 6. Scoop out a part of the middle from each half so that you have two potato cups.

Safety Precautions Not Applicable

SESSION: Link to known information/previous activity In the previous activity, we learnt about diffusion. Here, we will understand another important process for plants.

Procedure Explain to the learners that osmosis is like diffusion. The difference is that Osmosis describes the movement of only water molecules whereas diffusion describes movement of solid, liquid, or gas molecules.

Figure 6 – Potato osmometer

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Ask a few learners to help you with the experiment.

Take two shallow dishes. Fill both with water (about 2-3 inches deep). Place one potato cup in each dish.

Fill the inside of the first potato cup (about half) with sugar solution. Mark the level of the sugar solution in the cup with a pin. Ask learners to repeat the same setup but this time, ask them to fill water in the cup instead of sugar solution. Mark the level of water with a pin. This will serve as a control.

Leave this set up (both experiment and control) undisturbed for 15-20 minutes.

Now, Show the learners the two sets of raisins. One set soaked in water and removed and one set of dry raisins.

Ask them to touch and feel it and feel the difference.

Ask the leading questions and discuss.

After twenty minutes go back to the potato osmosis set up and ask students to observe the change and mark any change in the water level using a second pin and compare this to osmosis that took place in the raisins.

Note to Instructor: sometimes the potato osmosis may take upto 30 minutes. In this case, move on to the next ABL and come back to it later.

Leading Questions – Raisins 1.

2.

3.

4.

5.

6.

7.

What was the difference between the two types of raisins you saw? Why? How do you think water entered the raisin?

Why do you think other components do not leave the raisin through the skin?

Why do you think water went into the raisin and not out of the raisin?

If I put this raisin in a highly concentrated sugar solution, what do you think will happen?

Now based on these examples, what conclusion can you draw?

Can you now try to define osmosis with respect to movement of water molecules?

Discussion and Explanation 1. One set of raisins were swollen and the other set had dry, shrunken raisins because the first set had been put in water and had taken in a lot of water.

2. The water entered the raisins through their skin. This is called endosmosis.

3. The other molecules inside the raisin are too big to get out and hence the skin forms a selectively permeable membrane ,i.e, it only lets water through it.

4. In a very concentrated solution, the concentration of water molecules inside the raisin becomes more when compared to the region outside the raisin. So the water molecules move out of the raisin and the raisins begin to shrink again. This is called Exosmosis.

5. Based on this example, we can see that water molecules can move in and out of the raisin through the skin from a region where they are more to the region where they are less.

6. Osmosis is the movement of water molecules, through a selectively permeable membrane, from a region of their higher concentration to a region of their lower concentration. The skin of the raisins acts as a selectively permeable membrane. In osmosis transportation occurs across a semi permeable membrane. In imbibition transportation occurs through open pores. This is the difference between osmosis and imbibition.

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Leading Questions – potato osmometer 1. What changes do you observe in the experimental set up?

2. Why do you think this change in level occurred?

3. Do you think that sugar molecules get out of the potato and into the dish?

4. What does the potato act like in this experiment?

5. What is it selectively permeable for?

6. Can you think of any examples where a living thing may use this kind of process?

7. Can you think of any application of osmosis that can be used in our surroundings?

Discussion and Explanation 1. The level of sugar solution in the potato has gone up from the initially marked level but the level in the control potato cup has remained the same.

2. The water molecules from the beaker moved into the potato as their concentration was lower in the sugar solution.

3. No, the sugar molecules do not leave the potato cup. This is because the potato is selectively permeable and does not allow the sugar molecules to pass through. If you repeat this experiment in a very clean environment, you can confirm this point by tasting the water in the dish. You will find that it is not sweet.

4. The potato acts like a selectively permeable membrane 5. It is selectively permeable for water – This means only water molecules can pass through it. It does not let sugar molecules pass through it.

6. Plants use osmosis to absorb water through their roots. The human body also uses processes like osmosis in the kidneys to produce urine.

7. Preserving food. For thousands of years, perishable foods such as fish, olives, and vegetables have been preserved in salt or brine. When bacteria that spoil the food get into the concentrated salt solution, the water in them goes into the salt solution by osmosis. Because of this, the bacteria die before they can spoil the food.

KEY MESSAGES:   

Osmosis is the diffusion of water molecules across a semi permeable membrane.

Osmosis is a key process involved in transportation in living things.

Osmosis also has many practical applications in our surroundings today.

LEARNING CHECK: Ask learners to list the key things they have learnt. Guide them to the key messages listed and then put up the key messages chart. Use the learning check that is given at the end of ABL 1.4. This is to be done after completing ABL 1.4.

INTERESTING INFORMATION More examples of Osmosis in our daily life: Agastya International Foundation. For Internal Circulation only.

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



Artificial kidneys. People with kidney disease rely upon artificial kidney machines to remove waste products from their blood. Such machines use a process called dialysis, which is similar to osmosis.

The difference between osmosis and dialysis is that a dialyzing membrane permits not just water, but also salts and other small molecules dissolved in the blood, to pass through. These materials move out of blood into a surrounding tank of distilled water. Red blood cells are too large to pass through the dialyzing membrane, so they return to the patient's body.

Desalination by reverse osmosis. Oceans hold about 97 percent of Earth's water supply, but their high salt content makes them unusable for drinking or agriculture. Salt can be removed by placing seawater in contact with a semipermeable membrane, then subjecting it to great pressure.

Under these conditions, reverse osmosis occurs, by which pressure is used to push water from a more concentrated solution to a less concentrated solution. The process is just the reverse of the normal process of osmosis. In desalination, reverse osmosis is used to push water molecules out of seawater into a reservoir of pure water. This is similar to RO water purifier advertisements that we see on TV. Time: 20 min

ABL 1.4 LEARNING OBJECTIVE - What is active transport?

ADVANCE PREPARATION: Material List S. No. 1 2 3

Material

Quantity

Concentration gradient chart of activity – Chart 2 Toy cars

1 per class

Sloping surface (thick cardboard pieces – 2ft by 3ft)

6 per class 6 per class

Things to Do Not Applicable Safety Precautions Not Applicable

SESSION: Link to known information/previous activity

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In the previous activity we learnt about osmosis and the transportation of water, Now we shall explore situations where molecules have to move from lower concentration to higher concentration.

Procedure Divide the learners into six groups. Hand out one cardboard slope and one car to each group. Tell them to hold the cardboard like a slope and ask each of them to try releasing the car from the top of the slope and pushing the car up the slope. One they are done, collect the materials and have them all seated around you such that they can see the chart for discussion. (Use the chart only for explanation after all of the children has tried the activity.)

UNDERSTANDING THE ACTIVITY: Leading Questions 1. Which of the two activities required more energy?

2. Now, if we apply the same principle to concentration and say molecules are moving upwards (lower to higher) or downwards (high to low), which process do you think will require less energy?

3. Can you name a process where molecules move from higher to lower concentration?

4. Which process will require more energy?

5. In what direction does active transport occur with respect to diffusion?

Discussion and Explanation 1. It requires more energy to push a car up the slope than it does for the car to come down the slope.

2. Movement of molecules from higher to lower concentration will require less energy..

3. Osmosis and diffusion involve movement of molecules from higher to lower concentration.

4. It will require more energy for molecules to move from lower to higher concentration. Explain and show chart – this process is called active transport. It gets the energy from molecules like ATP, which store energy. (remind them that they learn about ATP in respiration) 5. Active transport occurs in a direction opposite to diffusion.

A concentration gradient is formed when there is a difference in concentration between two mediums that are in contact with each other. The gradient is measured/marked from lower to higher concentration. This is why it is said that diffusion takes place along the concentration gradient and Active transport takes place against the concentration gradient.

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Chart 2 – Concentration gradient chart

KEY MESSAGES:    

Active transport is the passage of a substance (salt or ion) from its lower to higher concentration.

Direction of Active transport is opposite to diffusion.

This uses energy from ATP to transport ions and molecules across a living membrane.

Active Transport is essential to transport food and mineral ions in many living things.

LEARNING CHECK: Ask learners to list the key things they have learnt. Guide them to the key messages listed and then put up the key messages chart. Now, carry out the following activity as a learning check for the information for ABLs 1.1 to 1.4.

What is the difference between diffusion, osmosis and active transport?

Materials for Learning Check: S. No. 1

2

Material

Quantity

Chart with differences – Osmosis, Diffusion and Active transport – Chart 3 Question cards

1 per class

10 per class

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Put up the chart with the differences and give the learners five minutes to go through them. Tell them you will have a quiz in teams after they are done. Divide the class into two groups. Ask each group to have a representative who will answer after discussion with the group. Each group will get a turn to answer and will pass if they do not know the answer. Right answers get 100 points and passed questions get 50 points.

Remove the chart before you start the quiz. Put up the question cards one by one as you ask the question

CHART:

DIFFUSION Liquids and gasses can diffuse over long distances

OSMOSIS Water only transported over short distances

Movement of molecules of solute or solvent Rapid in gasses but slow in others Transport from high to low concentration gradient

Movement of only water molecules Slow process

Occurs with or without a non-living permeable membrane No cell energy required Definition: transport of gasses or dissolved substances in solution from a region of higher concentration to region of lower concentration when the two are in direct contact

Transport of water molecules from region of their higher concentration to region of their lower concentration (dilute to concentrated solutions) Either a living or non-living semi-permeable membrane is needed No cell energy required Definition: transport of water through a semipermeable membrane from a region of their higher concentration (dilute) to a region of their lower concentration (concentrated).

ACTIVE TRANSPORT Certain specific solutes and ions are transported through short distances Movement of ions only Rapid process Transport of specific substances from a region of lower concentration to higher concentration against a concentration gradient A living selective membrane is essential Cell energy from ATP required Definition: Transport of a substance from low to high concentration region, using energy from cell through a living cell membrane.

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Note to Instructor: you can add more questions as per the table. Make one question card per question.

1. Which type of process is always a slow process?

2. Which type of process always occurs rapidly (fast)?

3. Which process can transport molecules across longer distances?

4. Which process does not require any membrane 5. Which process requires a living selective membrane?

6. Which process requires maximum energy?

7. Which is the process that occurs in a direction opposite to diffusion?

8. Which process transports only water molecules?

9. Which process involves movement of molecules from a lower to a higher concentration?

10. Which process requires ATP? Answers for Instructor’s reference: 1.

2.

3.

4.

5.

6.

7.

8.

9.

10.

Osmosis Active Transport Diffusion Diffusion Active transport Active transport Active transport Osmosis Osmosis Active transport

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ABL 2– Transport of food and water in plants Activity

Learning Objective

Key Messages  

2.1

Why do we need transportation in plants and what parts of the plant are involved in this transport?





2.2

What paths do water and food follow in the plant body?







2.3

How is water transported through the xylem?



Every cell in a plant needs energy, which it gets from food.

The plant makes its food using water from the soil, which is transported to the leaves. The leaves prepare the food and transport it to the rest of the plant.

Xylem and Phloem are pipe-like structures that are used to transport water and food in a plant respectively.

Time (min) 10

Water is taken up by the root and goes to the leaves through the Xylem. The Xylem has unidirectional flow, from ‘down to up’.

The leaf synthesizes food for the plant from this water and carbon dioxide absorbed from the atmosphere.

Food molecules go from the leaf to various parts of the plant through the Phloem. The phloem has bi-directional flow.

10

Root pressure, due to ion transport and transpiration pull, is the forces behind water transport in the Xylem.

Capillary action acts to transport water vertically upwards from the roots with adhesive and cohesive forces acting between molecules.

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

2.4

How is food transported through the phloem?



Sucrose (primary end product of photosynthesis) - Food goes into the phloem by using energy from ATP. This build up osmotic pressure inside the phloem and water flows along with the sucrose Tissues and cells of the plant have lower pressure and thus, food goes from the phloem into the tissues (TRANSLOCATION).

Total Time

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60

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Time: 10 min

ABL 2.1 LEARNING OBJECTIVE - Why do we need transportation in plants and what parts of the plant are involved in this transport?

ADVANCE PREPARATION Material List S. No. 5

Material Picture representations of 2,3 and 4 if microscope is not available – Flip chart

Quantity 6 sets per class

Things to Do Not Applicable Safety Precautions Not Applicable

SESSION Procedure We know that photosynthesis take place in the leaves. In this process, the plant prepares food. For this, the plant needs water and carbon dioxide as raw materials. How does the plant get these raw materials?

Divide the learners into groups of eight. Based on the above discussion, ask the learners to discuss the similarities between a tall building and a plant. Give them the leading questions on a chit so that they get an idea of what to discuss. Once they are done, take a few answers from the students and show them the microscopic images of Xylem, Phloem and root hair as per the discussion.

UNDERSTANDING THE ACTIVITY Leading Questions 1. How do you think water reaches a sink/bathroom in the building?

2. If I make some tasty food and I want to share it with someone on the 20th floor of the building, how do I go give it to him or her?

3. How do I go give something to somebody on the ground floor of the building?

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4. Similarly, in a plant, if the leaf makes the food, how do you think water from the soil comes up to the leaf?

5. Similarly, in the plant, how do you think the food is transported from the leaf to the rest of the plant?

Discussion and Explanation 1.

2.

3.

4.

The water reaches the bathroom by the use of pipes that are present in the building One will take the lift to the 20th floor.

One will take the lift to the ground floor Pipe like structures (like the water pipes in the building), called xylem, transport water from the soil to the leaf(Note to Instructor – show learners images of section of xylem tissue and root hair) 5. Pipe like structures(similar to the lifts), called phloem, transport food from the leaf to all parts of the plant (Note to Instructor – show learners images of section of phloem tissue) Note to Instructor – explain to students that the tall building does not mean that this transport system is only for tall trees and plants but it works universally for all plant life.

KEY MESSAGES:   

Every cell in a plant needs energy, which it gets from food.

The plant makes its food using water from the soil, which is transported to the leaves. The leaves prepare the food and transport it to the rest of the plant.

Xylem and Phloem are pipe-like structures that are used to transport water and food in a plant respectively.

LEARNING CHECK: Ask learners to list the key things they have learnt. Guide them to the key messages listed and then put up the key messages chart. If you have time during the class, make up a small game or quiz or match the following as a learning check. This may have to be done as part of advance preparation.

ABL 2.2

Time: 10 min

LEARNING OBJECTIVE - What paths do water and food follow in the plant body?

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ADVANCE PREPARATION Material List SL.NO. Material 1 Student worksheet – Worksheet 1

Quantity 20 per class

2

Large laminated worksheet for instructor (can be wiped and reused) – Worksheet 1

1 per class

3

Red and blue white board marker

4

Red and blue sketch pens

1 set per class 20 sets per class

Things to do N/A Safety Precautions Not Applicable

SESSION Link to known information/previous activity In ABL 2.1 we learnt that the xylem and phloem transport food and water. Here we shall explore how the food and water move through the plant through an activity. Keep in mind how the transport occurred in the example of the building.

Procedure Ask the learners to form pairs. Give each pair a worksheet and sketch pens. Ask them to mark the direction of food and water flow on the diagram of the plant. Tell them that the red pens should be used to mark the phloem tissue and hence the path of food will be indicated using red arrows. Similarly the path of water and the xylem tissue will be marked with blue pens. Ask them to discuss their work and plan it out before using the sketch pens.

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After five minutes, tell learners that you will draw out the arrows on the sample sheet and they can check their work. As you mark the arrows, ask leading questions and take help from the learners to finish marking the arrows. Give students two minutes to correct their own work.

Figure 7 – Direction of flow in Xylem and Phloem (for Instructor’s ref.)

UNDERSTANDING THE ACTIVITY Leading Questions 1.

2.

3.

4.

5.

Where is the food made? Where is it transported to? How? Does the food in the phloem go in one direction or many?

Where is the water taken from? Where is it transported to? How? Does the water in the Xylem go in one direction or many?

Do the xylem and phloem cross paths?

Discussion and Explanation 1. Food is made in the leaves and is transported to all parts of the plant through the phloem.

2. The food in the phloem goes upwards and downwards to reach all parts of the plant. (bi-directional flow) 3. The water is taken from the ground by the roots and is transported to the rest of the plant (especially the leaves) through the Xylem.

4. The water only travels upwards through the xylem. Hence, flow is uni-directional 5. No, the xylem and phloem do not cross paths.

KEY MESSAGES 

Water is taken up by the root and goes to the leaves through the Xylem. The Xylem has unidirectional flow, from ‘down to up’.

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 

The leaf synthesizes food for the plant from this water and carbon dioxide absorbed from the atmosphere.

Food molecules go from the leaf to various parts of the plant through the Phloem.The phloem has bi-directional flow.

LEARNING CHECK: Ask learners to list the key things they have learnt. Guide them to the key messages listed and then put up the key messages chart. If you have time during the class, make up a small game or quiz or match the following as a learning check. This may have to be done as part of advance preparation.

Time: 30 min

ABL 2.3 LEARNING OBJECTIVE –How is water transported through the xylem?

ADVANCE PREPARATION: Material List Sl.No.

Material

Quantity

1

Root hair and cells chart – Chart 5

1

2

Glass or beaker

3

3

Food colouring

3 colours

4

3

5

Flowers (Canna or Carnation or Rose) –with white petals Stirrer

6

Capillary

6

7

Straw

6

8

Glass/paper cup

6

8

Glass slides

6

10

Petri dish

3-6

11

Thermocol balls

6

1

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Things to Do For SESSION 2.3b: Set up the transpiration pull experiment one day or at least 12 hours before the class. https://www.youtube.com/watch?v=ZLLe5Bw8evY 1) Take a beaker or a glass tumbler 2) Pour one cup of water in it and add 20-30 drops of food colouring to it.

3) Take awhite flower (Canna or Rose or Carnation) and cut off the base of the stem and place it in the glass.

4) Replicate this with 2-3 colours if possible 5) Keep the set up aside for 12 to 24 hours Safety Precautions

Not Applicable

SESSION: SESSION 2.3a Link to known information/previous activity – In the previous ABL we learnt about the forces involved in transportation of water and food in a plant. Now we will see how exactly a plant uses these forces to effectively transport water.

Note to Instructor: Quickly revise the concentration gradient chart and three main types of transport – Osmosis, diffusion and active transport in case you have not done previous ABL. Procedure Explain the following to the Learners: You have learnt that the roots transport water in the plant with the help of Xylem vessels. You have also learnt the various forces involved in transportation of water. Let us now understand how these forces are used by the Xylem. (You can use the plant shown in chart - 5 to explain this). For this, you will study the cellular structure of the xylem and root hair.

Explain to them that by analysing howeach cell takes up water and transfers it to the next cell, they can understand how the entire plant receives water. Explain that they will also see how other processes, like ion/mineral transport are related to water transport. Show them the chart of the root hair in the soil and ask leading questions.

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Chart 5 – Root hair and cells

UNDERSTANDING THE ACTIVITY: Leading Questions 1. Where are water and minerals for the plant coming from?

2. When the plant needs minerals/ions it takes it up from the soil. The roots already have more minerals inside than the soil. (Show in the chart). So now can you guess which transport system the plant will use to take up ions?

3. Now we see that the ion concentration inside the root hair cell is very high. So what do you think happens to the water molecules in the soil? Which process is involved?

4. Now, that the concentration of water in the cell near the soil is high, what do you think happens to that water? (clue – the cell walls are semi permeable)

Discussion and Explanation 1. The plant gets water and minerals from the soil through the roots.

2. Ions/minerals have to go from their region of lower concentration (soil) to higher concentration (roots).We know that a movement against the concentration gradient requires energy. Hence, ions are taken in by active transport.

3. The high concentration of ions inside the root hair sets off the process of osmosis which causes water from the soil to diffuse into the root hair.

4. The cell in contact with the root hair again takes up the water from it by the process of osmosis through the semipermeable cell wall.

5. EXPLAIN – In this manner, a chain reaction continues and water continues to pass to cells that are next to each other till it finally reaches the xylem. This build-up of water pressure causes the water to enter the xylem vessels with a lot of force, which will push the water up the xylem channel to the Agastya International Foundation. For Internal Circulation only.

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rest of the plant. For taller plants however, this root pressure alone is not enough to transport water to the top of the plant.

KEY MESSAGES:   

Root pressure is one of the forces responsible for water transport in plants.

Root pressure is built up in the roots due to inflow of water from the cells (due to osmosis) to the xylem.

Root pressure helps in pushing cell-sap upwards.

SESSION 2.3b Link to known information/previous activity – In the previous activity we learnt about root pressure.Now we will learn about other factors that help the transportation of water in plants.Ask learners to recollect what they have learnt about transpiration pull from the Photosynthesis chapter.

Procedure Show learners a normal flower and then show them the flower in the experimental set up. Use leading questions to discuss the concept of transpiration pull by comparing the two flowers.

UNDERSTANDING THE ACTIVITY: Leading Questions

1.

2.

3.

4.

5.

What is the difference between the two flowers?

How did the flower take up the colour?

So how do you think the water was transported all the way to the petals?

Where does the water from the leaves and petals go?

If we have root pressure already, why do we need transpiration pull?

Discussion and Explanation

1. One flower has plain white petals and the other one has colour in it.

2. The petals of the flower got the colour from the water.

3. The water is taken up by the flower stalks through the xylem and transported to the leaves and petals.

4. Once the water reaches the leaves, some of it is lost to the atmosphere by a process called transpiration. EXPLAIN - This creates a need for more water to be pulled up by the leaves and so exerts a force or a pull. This, pull or force that makes the water come up the xylem is called transpiration pull.

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5. In some tall plants and trees, root pressure is not enough for a plant to transport water up the xylem till the top. Hence, transpiration pull comes into play.

KEY MESSAGES: 

As water is lost by transpiration, a suction force is created by the leaves that pulls water up the xylem  This is very important in tall plants and trees where root pressure is not enough to transport water in the xylem

SESSION 2.3c Link to known information/previous activity – In the previous activity we learnt about transpiration pull.Now let us how and why water moves up in the xylem.

Procedure Explain to the learners that they will perform different experiments in groups to understand how capillary action works. Divide the learners into three big groups. Within each group have them divide themselves into three groups A, B and C. Tell them that at any point of time only one of the three sets will perform an experiment and the other two will observe. In this way each group will get to perform one experiment.

All experiments can be performed at a go and the discussions can all be done after.

Experiment for A group – Glass slide experiment[ B and C observe] Give each group two glass slides, a small piece of a splint or a needle and two rubber bands. Ask the learners to bind the two slides together with a small gap in between them. They can create this gap by keeping the needle/splint between the slides and they can secure the slides using the rubber bands. Ask them to then fill a little coloured water upto about 2 inches in the petri dish and then push one end of the slide arrangement quickly into this water. Ask learners to observe what happens.

Figure 8 – Glass slide experiment A

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Figure 9 – Glass slide experiment B

Experiment for B group – straw v/s capillary [A and C observe] Give the learners a clear plastic cup, a straw, a capillary and food colour. Have the students fill the cup will coloured water upto 3 inches and then push one end of the straw quickly into the water and observe what happened. Now, ask them to remove the straw and repeat the same action with the capillary and see what happens. (they can block one end of the straw with their finger n then release it on dipping the other end.

This will show better results)

Figure 10 – Capillary experiment Experiment for C group – thermocol ball experiment [A and B observe] Give the learners a clear plastic cup, some thermocol balls and some water. Tell them to fill the cup half with water and then drop the balls onto the surface and observe how the balls act. Now slowly pour more water into the cup (along the sides) till it is almost at the brim/just about to overflow and observe how the balls act.

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Figure 11 – Thermocol ball experiment

UNDERSTANDING THE ACTIVITY: Leading Questions (glass slide experiment) 1. What did you observe?

2. Why do you think this happened?

Discussion and Explanation 1. The water rises up into the gap between the slides to a level higher than the water in the petri dish.

2. This is called capillary action. This occurs due to the attraction of the water molecules to the glass slide as well as to other water molecules. These will be explained better in the next few experiments.

Leading Questions (straw v/s capillary) 1. Which of the two tubes required lesser force?

2. Why do you think the capillary needs lesser force for water to rise?

3. How do you think this helps the plant?

Discussion and Explanation 1. The capillary requires lesser force to make the water rise 2. This is due to the relatively small thickness of the capillary when compared to the straw 3. The xylem vessels in the plant are like capillaries and hence can conduct water to great heights from the roots even with a small force like transpiration pull.

Figure 12 – Capillary action Leading Questions (Thermocol ball experiment) 1.

2.

3.

4.

What did you observe in the first case? Why? What did you observe when water was added? Why? How is this similar to what happens in a xylem vessel?

Where else do we see adhesive and cohesive forces in our environment?

Discussion and Explanation

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1. In the first case, the thermocol balls all collected towards the sides of the cup. This is because they are attracted to the molecules that make up the cup. This attraction which causes one type of molecule to attach to another type is called adhesive force.

2. When the water level goes up, the balls are forced away from the wall and they suddenly cling to each other. This attraction which causes one type of molecule to attach to another molecule of the same type id called cohesive force.

3. In plants, these forces come into play when water is transported in a xylem vessel. Water molecules are attracted to the walls of the xylem by adhesive forces and the water moves upwards at each water molecule is attracted to the ones above it by cohesive forces.

Figure 13 – Adhesion and cohesion 4. Observe droplets of water on the surface of a leaf.

Figure 14 – Adhesion and cohesion - leaf

KEY MESSAGES:  

Root pressure, due to ion transport and transpiration pull, are the forces behind water transport in the Xylem.

Capillary action acts to transport water vertically upwards from the roots with adhesive and cohesive forces acting between molecules.

LEARNING CHECK: Ask learners to list the key things they have learnt. Guide them to the key messages listed and then put up the key messages chart. If you have time during the class, make up a small game or quiz or match the following as a learning check. This may have to be done as part of advance preparation.

TRY IT YOURSELF https://www.youtube.com/watch?v=mdkeZbm0cCI Agastya International Foundation. For Internal Circulation only.

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Figure 15 – Capillary transfer experiment This try at home activity involves transferring water from one cup to another by capillary action through a paper towel. Ask them to think about what adhesive and cohesive forces acted in transporting the water from the lower cup to the higher.

ABL 2.4

Time: 10 min

LEARNING OBJECTIVE – How does food travel in the phloem?

ADVANCE PREPARATION Material List SL.NO. Material 1 Potted plants 2 Chart on food transport 3 Microscopic cross section image of phloem

Quantity 2 1 3-4

Things to do Cut out a girdle from one plant as per the explanation in the picture below and leave it for a few weeks.

This plant can then be used repeatedly.

Cut a ring around the stem of the plant and remove the outer layer and cambium but leave the xylem intact as shown in the diagram. Let the plant remain in the pot. Leave it for a few weeks. It will then be observed that a part of the stem above the ring has grown in diameter. The part below will look undernourished and dead but the upper part has healthy leaves.

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Figure 16 – Girdling of a Plant Safety Precautions Not Applicable

SESSION Link to previous activity In the previous activities we learnt that the xylem transport water. Here we will explore how the phloem transports water through the plant.

Procedure Show students the two plants and explain what you did to the plant with the girdle. Ask them leading questions and discuss to show how the phloem transports the food.

UNDERSTANDING THE ACTIVITY Leading Questions 1.

2.

3.

4.

5.

6.

What difference do you see between the two plants?

Why do you think the upper portion of the plant is swollen above the cut?

Why do you think the portion below the cut looks weak and is not swollen?

How come the leaves in the upper portion are still standing stiff and healthy?

What does this tell us about the positions of the xylem and phloem within the stem?

So, is the direction of flow of food in the phloem uni/bi-directional?

Discussion and Explanation 1.

2.

3.

4.

5.

The second plant has a swollen stem above the cut.

The upper portion has accumulated sugars and other nutrients as it is oozing sap.

The portion below the cut does not get enough food supply and hence, is weak and dying.

The leaves in the upper portion are still getting a healthy supply of water in spite of the cut.

This means that only the phloem seems to have been cut and the xylem must be intact. So, most often the xylem vessels are present inwards, towards the centre of the stem and the phloem vessels are located toward the outside of the stem.

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6. The flow of food in the phloem is bi-directional. (Explanation– illustrate phloem cells again by showing the microscopic section image and tell them the phloem cells are called sieve tubes.)

7. Use chart to explain how the phloem conducts food through the sieve tubes. Explain that ions move from the soil into the phloem by active transport which creates a concentration difference. This concentration gradient initiates osmosis. Explain that this is active transport taking place that leads to osmosis. This transport is also called translocation.

KEY MESSAGES:  

Sucrose (primary end product of photosynthesis) - Food goes into the phloem by using energy from ATP. This build up osmotic pressure inside the phloem and water flows along with the sucrose Tissues and cells of the plant have lower pressure and thus, food goes from the phloem into the tissues (TRANSLOCATION).

LEARNING CHECK: Ask learners to list the key things they have learnt. Guide them to the key messages listed and then put up the key messages chart. If you have time during the class, make up a small game or quiz or match the following as a learning check. This may have to be done as part of advance preparation.

INTERESTING INFORMATION Xylem vessels consist of dead cells. They have a thick, strengthened cellulose cell wall with a hollow lumen.

On the other hand, phloem consists of columns of living cells

Figure 17 – Xylem and phloem 

Diagram showing the cross sections of a xylem and a phloem While the phloem is made up of living tissue, the xylem tissues die off at the end of each growing season and reform with the next, which is why you can see growth rings on the stump of a chopped tree. The phloem keeps working even during the dormant season, so it consists of living tissue.The concentric rings formed by the dead xylem accumulate in the plant and are called annual rings and can tell us a lot about the age and life of the tree/plant.

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Reading between the Rings Note to Instructor – Make a flip chat of images below for this discussion A cross section of a tree shows much more than its age! Diameter growth is particularly sensitive to fluctuations in the environment: moisture in the soil and air, temperature, and sunlight. Very broad rings generally indicate a good growing year. The tree apparently received everything it needed.

The growth rate of a tree can be compared to the growth of a child. A young sapling grows much faster than an adult tree. A cross section of an older tree shows rings that are quite broad at the beginning of its life (in the centre) but that become progressively smaller. An old tree produces very narrow rings and its diameter and height growth are considerably slower.

Look carefully at the pictures and read the explanation to understand what may have caused the cross section.

Flip chart 6 – Image 1 Narrow rings do not only signify a lack of sun or water. A forest fire may have damaged the tree's crown and slowed its growth. Defoliation by insects or fungi can have the same effect.

After several years, the tree gained strength and returned to normal growth.

Flip chart 6 – Image 2

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This tree had a rough time during its first ten years! Maybe someone helped it by cutting the large trees around it to give it more light.

Flip chart 6 – Image 3 This tree shows off-centre growth. If the tree was in a location exposed to high winds, its wood would grow faster (wider rings) on the side away from the wind than on the side facing the wind.

This cross section may also come from a tree that was leaning. The tree formed reaction wood (compression wood) that enabled it to straighten up. The wider rings are on the underside of the leaning trunk because growth was faster there.

Flip chart 6 – Image 4 Do you see waves? Look at the outer bark. Wasn't there a branch here?

REFERENCES: 1) National Council of Educational Research and Training, Class X, November 2012.

2) Concise Biology, Part I – Class IX, H.L Gupta for Selina Publishers, January 2003.

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